Presently known magnetic disk drives are widely used for data storage. A disk drive includes one or more disks mounted on a spindle, and a head arm assembly for accessing data tracks on the disk during seek, write and read modes. The head arm assembly includes a load beam and a head gimbal assembly. The gimbal assembly comprises an air bearing slider pivotally attached to a flexure. A magnetic transducer for interacting with the storage disks, is supported by the slider.
During the data seeking mode for example, the disks spin at a high speed about the spindle. The aerodynamics between the slider and the disk surface provides sufficient buoyancy to the slider to fly above the disk surface. On the other hand, the spring force of the resilient load beam pushes the slider toward the disk surface. As a result, an equilibrium point is reached in which the slider flies over the disk surface at a very close spacing, which is the flying height of the slider.
A small flying height provides many advantages and is a major goal for most magnetic head suspension assembly designs. For example, data error is substantially reduced as data can be more reliably written onto or retrieved from the storage disks during the respective write and read modes. Also, the smaller flying height enables recording narrow data track widths, with resultant higher storage capacity.
There are problems associated with reducing the flying height of the slider. The topology of the disk surface, though highly polished, is not at all uniform at microscopic scale. Very often, the disk surfaces are not rotating about the common spindle at a perfectly perpendicular angle. A minute angular deviation would translate into variations in disk-to-slider distances while the disk is spinning. For reliable data writing and reading, the load beam must carry the slider in a manner that the slider can faithfully follow the topology of the disk surface through the thin air film separated the spinning disk and the slider. Accordingly, the magnetic head suspension assembly, including the load beam, must be sufficiently flexible to accommodate the uneven disk surface contour. The suspension assembly must also be reasonably robust to resist any physical deformation caused by the rapid movement of the actuator arm.
A rigidly built load beam is inflexible and is therefore ineffective to maintain a small flying height. On the other hand, a load beam made too flexible is more apt to resonate at a low frequency. Furthermore, a highly flexible load beam is more susceptible to deformation. A deformed load beam, would be prone to resonate at a still lower frequency and is detrimental to the performance of the magnetic head.
The problem of shock resistance is also of concern in the design of a magnetic head suspension. For a disk drive during the state of nonuse, the actuator arm is normally parked at a designated track on the disk surface. This is commonly called the "parking position" of the magnetic head. To reach the parking position, the actuator arm moves the slider above the parking track. The spinning disk then decelerates. The slider loses air buoyancy and slowly lands on the parking track. The slider rests on the parking track until the next takeoff for accessing tracks to read or write data or if it experiences mechanical shock. In the latter case, the impact of the shock would momentarily separates the slider from the disk surface. Thereafter, the slider will bounce back and collide with the disk surface caused mainly by the spring force of the load beam. The impact and bounce actions all happen within a short period of time. The collisions can damage the magnetic head and render the entire disk drive inoperable.
The shock is commonly called the "separation shock" and the unit of measure is in g's/gram where g is the gravitational acceleration in vacuum. A rigid load beam provides a higher separation shock. However, the flexibility and agility of the load beam are also compromised.
A typical prior art load beam described above is illustrated in FIGS. 5 and 6. A load beam with a narrow width is used to address the problem of resonant vibrations at low frequencies. The mass of the load beam is correspondingly reduced resulting in a load beam with higher resonant frequency. However, the problem with this approach is that the lateral stiffness of the load beam is also sacrificed. A load beam with low lateral stiffness is more vulnerable to deformation. Once the load beam is deformed, the resonant frequency is greatly reduced. Moreover, a narrow and elongated load beam, such as illustrated in FIGS. 7 and 8, cannot withstand a high separation shock.